There is a very extensive literature on Euler-Poisson-Darboux equation, that is equation (REF ) with \(A(x,\partial _x)\)  \(=\Delta \)  (see, e.g., [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]} and bibliography therein). In particular, Wirth [8]} used Bessel functions to represent the solution of Euler-Poisson-Darboux equation. In [11]} the version of the integral transform approach [12]}, [13]} was employed by Palmieri for the derivation of the integral representation formulas for the solution of a linear equation with the coefficients, which are scale-invariant and independent of \(x\)  variable. Then Palmieri and coauthors [14]} applied these formulas to examine the blowup phenomena for the wave equations with different types of nonlinearities in the spacetime with power type expansion.
